I have a 2 part question that hopefully has a simple answer. Firstly, I'm going to purchase an iMac which will be used primarily for photo editing via Aperture 3, Photomatix, PS CS5, and various editing plugins such as Nik Software and Topaz. I am between the 21.5" and 27" model and not because of screen size. The 27" can be upgraded to 16GB of RAM while the 21.5" can only go to 8 gigs. Would 8 gigs suit me just fine for this purpose while 16 gigs would be overkill or would I see substantial gains from 16 gigs of RAM? Part 2 is I am interested in purchasing a Drobo as well. Aside from being a backup for my photos, can you house your work on the Drobo while making edits to these referenced files in Aperture/PS/etc? Trying to figure out if I would need to upgrade the base 1TB HD to a 2TB drive. Sorry for the long post, but any help is gratefully appreciated.